1. Field of the Invention
This invention relates to spinal fixation and methodology and more particularly to an improved spinal support fixation and method for the surgical treatment of spinal problems which may require correction, stabilization, adjustment of fixation of the spinal column or components thereof, and more particularly the lumbar and sacral portion of the spine, although the present invention is not limited thereto and may be used in the thoracic region of the spine.
2. Description of the Prior Art
Various types of spinal column disorders are known such as scoliosis, kyphosis, spondylolesthesis and other problems such as ruptured or slipped discs, broken or fractured spinal column, and the like. Various forms of instrumentation and procedures are known for the surgical treatment of spinal disorders, for example, Harrington Spiral Instrumentation, Bobechko Hooks, Edwards Hooks and Rod Sleeves, Luque Segmental Spinal Instrumentation and Luque Rectangles, the Dunn Anterior Spinal System, and the Kostuik-Harrington Instrumentation, to mention only a few. These and other systems are described in one or more of the following U.S. Pat. Nos.: 4,433,676; 4,369,769; 4,269,178; 4,409,968; and 4,289,123.
Some of the above systems utilize hook-type members which are merely hooked over the laminae or on selected transverse processes of the spine. Other systems, such as the Luque Segmental Spinal Rectangles, used to stabilize spinal fractures and low back fusions, use Luque wires to secure the rectangle to the spine. In some of the prior art systems, screws are used to hold a single rod in place. In other systems, screws are used to hold a slotted plate in place, the location of the screws and slots being such that the plate is moved in order to align the plate apertures or slots with the end of the screw, a nut being used to hold the plate to the screw. With this latter arrangement, sometimed referred to as a Steppee plate, there is little purchase between the plate and the screw and nut since only a small portion of the plate is engaged adjacent to the slots. Also, the plate cannot be configured to a fixed and stable curvature to follow the curvature desired by the surgeon.
As a general rule, in any of the procedures requiring the use of fixation of the type described, it is desirable to prevent rotation of the vertebral body while preventing left to right and back to front motion, in order to promote effective healing. In the case of spinal fusions for example, the fixation may be in place for six to twelve months or longer and must function properly and effectively for that period of time. If the fixation becomes loose or falls out of adjustment, it is somewhat difficult to make the necessary adjustments due to the nature of the prior art fixation. Adjustment or modification of the prior art fixation may be as major an undertaking as the original installation of the fixation due to the necessity to loosen wires or adjust hooks or rods. If, for example, a patient experiences significant pain as a result of the initial and skillful placement of the support fixation, even a minor adjustment of the prior art fixation may represent a major undertaking.
Another difficulty with the prior art fixation is that it is sometimes difficult to cause the spinal column to follow the correct or desired contour. For example, the rods used in the Harrington system or the variations thereof are normally straight rods or curved in one plane only. It is sometimes difficult to locate hooks intermediate the ends of the rod so that the vertebra between the ends of the rods are in the proper position simply because of the difficulty in properly positioning the intermediate hooks and/or forming and fixedly supporting the rods to follow the desired contour. It has been reported, for example, that Knodt rods, alar hooks or sacral bars in adult L-S fusions is associated with failure of fixation, loss of lordosis and/or nonunion in 15% to 65% of the cases. In the case of lumbo-sacral fixation, present techniques have been criticized as not providing secure fixation directly to the sacrum, not providing preservation of normal L-S angle upon distraction or compression, or not providing rigid fixation in all planes of motion.
It is also recognized that the stresses involved in the sacral and lumbar regions of the spine are greater than those in the thoracic region of the spine, i.e., T1 to T14.